Lateral light propagation in SSFLC devices and thermal nonlinearities Jeroen Beeckman, Katarzyna Chałubińska and Kristiaan Neyts Liquid Crystal & Photonics group, ELIS Department, Ghent University St-Pietersnieuwstraat 41, B-9000 Gent, Belgium (E-mail:
[email protected]) Optical nonlinearities in nematic liquid crystals are well investigated in the last decade due to their huge nonlinear coefficients. Experiments either focus on the writing of holographic gratings [1] (by launching light beams perpendicular to the glass plates) or on the generation of spatial solitons [2]. In the latter case, the laser beam is propagating in the liquid crystal parallel to the glass plates. In this contribution we investigate the lateral propagation of laser beams in SSFLC cells and the induced nonlinearities. To our knowledge, besides some theoretical predictions [3], no experimental results have been reported on this subject. In our experiment, a Gaussian beam with a waist of 3 µm is launched into a SSFLC cell. In the liquid crystal the beam is visible due to scattering of light towards the observer (a). For optical powers of about 300 mW an island of isotropic material is formed. In the isotropic phase, the scattering of the beam is almost zero and we observe a dark region (b). Polarizing microscopy (filtering out the laser light) confirms that there is a region with isotropic phase (c) near the maximum intensity of the laser beam. The region is surrounded by outer shells consisting of the lower temperature phases. We believe that spatial solitons may be generated in these cells by tuning different parameters.
(a)
(b)
(c)
[1] Khoo I.C., “Liquid crystals: Physical properties and nonlinear optical phenomena”, New York, Wiley, 1995, p. 154 [2] Beeckman J., Neyts K., Hutsebaut X., Cambournac C. and Haelterman M., “Simulations and experiments on self-focusing conditions in nematic liquid-crystal planar cells”, Opt. Express 12, pp. 1011-1018, 2004 [3] Srivatsa S.K. and Ranganath G.S., “New nonlinear optical processes in liquid crystals”, Opt. Comm. 180, pp. 349-359, 2000 Acknowledgments: FWO-Vlaanderen, Research Training Network SAMPA, Photon Network IAP5/18
180
C33
